Simple-Sequence Repeat Marker Analysis of Genetic Relationships
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JOBNAME: horts 44#1 2009 PAGE: 1 OUTPUT: December 29 22:22:52 2008 tsp/horts/180127/03204 HORTSCIENCE 44(1):27–31. 2009. many of the H. paniculata cultivars available in the United States are relatively recent intro- ductions, little is known about their parent- Simple-sequence Repeat Marker age. In addition to named cultivars, a few wild-collected H. paniculata accessions are Analysis of Genetic Relationships available in the United States. Two of these were collected in Taiwan and appear to be the within Hydrangea paniculata only H. paniculata germplasm in the United States that was not either introduced from Sandra M. Reed1 Japan or bred from Japanese germplasm. USDA-ARS, Floral and Nursery Plants Research Unit, Tennessee State Microsatellite, or simple-sequence repeat University Otis L. Floyd Nursery Research Center, 472 Cadillac Lane, (SSR), markers provide a useful method for characterizing genetic diversity within a plant McMinnville, TN 37110 species. SSR markers were recently used to Timothy A. Rinehart study relationships among 114 H. macro- phylla (Thunb.) Ser. genotypes (Reed and USDA-ARS, Southern Horticultural Laboratory, 810 Highway 26 West, Rinehart, 2007). Genetic similarities were Poplarville, MS 39470 found among remontant, variegated, and Additional index words. breeding, molecular markers, panicle hydrangea double-flowered cultivars. Some presumed synonyms were valid, whereas others were Abstract. Genetic diversity studies using 26 simple-sequence repeat (SSR) markers were not. Potentially unexploited sources of germ- conducted with 36 cultivars, breeding lines, and wild-collected accessions of Hydrangea plasm within H. macrophylla were identified. paniculata Sieb. The SSR markers were highly variable among the genotypes, producing The objective of this study was to use SSR a mean of 5.8 alleles per marker. Three cultivars (Boskoop, Compact Grandiflora, and markers to study genetic relationships within Webb) were either identical to or sports of the popular cultivar Grandiflora. The name H. paniculata. We were particularly inter- ‘Pee Wee’ appears to have been applied to two phenotypically different compact forms of ested in rectifying synonym confusion and H. paniculata, one of which seems to be a sport of ‘Tardiva’, whereas the other is likely possible mislabeling errors and studying derived from ‘Grandiflora’. No close genetic similarity was observed among several relationships between cultivars developed cultivars from a long-term Belgium breeding program, although many had one parent in through the same and different breeding common. Early-flowering genotypes clustered separately from genotypes that flower in programs. midsummer, but close genetic relationships were not observed among early-flowering cultivars. Two genotypes from Taiwan were genetically similar but were distinctly Materials and Methods different from the Japanese genotypes. These, along with the early-flowering genotypes and a new collection from Japan, may represent unexploited sources of germplasm for Plant materials. The 36 H. paniculata improvement of H. paniculata. genotypes tested in this study are listed in Table 1. In addition to 28 cultivars, four wild- collected genotypes (BSWJ 3802, DJHT The genus Hydrangea L. consists of 23 loid, tetraploid, and hexaploid forms of 99157, HC 970618, PI 479429) and four species and has an American–Asiatic distri- Hydrangea paniculata have been reported, breeding lines (BL 16-02, BL 22-02, G-881, bution (McClintock, 1957). Several species but only the tetraploid chromosome number NA 74383) were examined. Twelve cultivars are cultivated as ornamentals, of which H. (2n =4x = 72) has been reported for horti- (Brussels Lace, Floribunda, Grandiflora, paniculata is the most cold-hardy (Dirr, cultural forms of the species (Funamoto and Greenspire, Kyushu, Limelight, Pink Dia- 2004). This species, which is also known by Ogawa, 2002; Funamoto and Tanaka, 1988; mond, Praecox, Silver Dollar, Tardiva, the common name of panicle hydrangea, is Haworth-Booth, 1984; Sax, 1931; Van Laere Unique, and White Lace) included in this native to Japan, eastern and southern China, et al., 2008; Zonneveld, 2004). study have been reported to be tetraploids and Taiwan (Dirr, 2004; McClintock, 1957). Hydrangea paniculata is cultivated pri- (Sax, 1931; Van Laere et al., 2008; Zonneveld, McClintock (1957) placed H. paniculata in marily as a garden plant, but there is also 2004); ploidy level has not been reported for Section Hydrangea Maxim., Subsection Het- interest in using it in the cut flower industry any of the other genotypes. A single plant was eromallae Rehder, along with H. heteromalla (Leeson et al., 2004). Most forms grow 3 to used for 26 H. paniculata genotypes. Three D. Don. Molecular data supported the rela- 4.5 m in height with a similar spread and seedlings of G-881, obtained from open- tionship between these two species and also produce long (15 to 20 cm) panicles in mid- pollinations of ‘Dharuma’, and two seedlings indicated that they share considerable genetic summer. Like with most other members of of DJHT 99157 were analyzed; data from similarity with Schizophragma Sieb. and the genus, H. paniculata inflorescences con- these plants are presented individually. Two Zucc. (Rinehart et al., 2006). Diploid, trip- sist of a combination of small, inconspicuous or three plants each of ‘Brussels Lace’, perfect flowers and large, imperfect flowers ‘Chantilly Lace’, ‘Floribunda’, ‘Grandiflora’, with showy sepals. Flowers open white or ‘Greenspire’, ‘Tardiva’, ‘Unique’, and cream-colored, but in some cultivars turn ‘White Moth’ were analyzed; because all Received for publication 25 Aug. 2008. Accepted for publication 7 Oct. 2008. pale to deep pink as they age. Rated as hardy duplicate samples of these cultivars yielded We thank David Creech and Barbara Stump (Mast to between –34 to –37 C (Rose et al., 2001), comparable data, data from only one repre- Arboretum at Stephen F. Austin State University), H. paniculata is recommended for USDA sentative are presented. Plant tissue was Kristin VanHoose (Amethyst Hill Nursery), Don cold-hardiness zones 4 to 8 (Dirr, 2004). obtained from plants in our collection at the Shadow (Shadow Nurseries), and Mark Widrlech- Approximately 50 extant cultivars of H. Nursery Research Center in McMinnville, ner (North Central Regional Plant Introduction paniculata have been described (Dirr, 2004; TN, or from public or commercial sources Station) for graciously donating tissue and plants Mallet, 1994; Mallet et al., 1992; van Gelderen (Table 1). Four H. heteromalla selections from their collections for this research. and van Gelderen, 2004). A few (‘Flori- were included in the analysis for rooting the Mention of trade names or commercial products in bunda’, ‘Grandiflora’, ‘Kyushu’, ‘Praecox’) phenogram. this article is solely for the purpose of providing specific information and does not imply recom- originated in Japan and have been in cultiva- Simple-sequence repeat development and mendation or endorsement by the U.S. Department tion for over 100 years. Many others were sample processing. Previously described of Agriculture. developed through breeding efforts in Europe SSR-enriched libraries (Rinehart et al., 1To whom reprint requests should be addressed; and have been introduced to the United States 2006) were screened for polymorphic loci e-mail [email protected]. only during the past 10 to 15 years. Although against a panel of 12 H. paniculata cultivars. HORTSCIENCE VOL. 44(1) FEBRUARY 2009 27 JOBNAME: horts 44#1 2009 PAGE: 2 OUTPUT: December 29 22:22:56 2008 tsp/horts/180127/03204 Table 1. Hydrangea paniculata genotypes evaluated with 26 simple-sequence repeat markers and sources of tissue. Source of leaf Expected Genotypes tissuez heterozygosity Big Ben NRC BL 16-02 MAST BL 22-02 MAST Boskoop NRC Allelic Brussels Lace AHN; NRC richness BSWJ 3802 MAST Burgundy Lace NRC Chantilly Lace MAST; NRC Compact Grandiflora MAST Dharuma NRC (bp) DJHT 99157 NRC Dolly NRC Allele range Quick Fireä (Bulk) SN Floribunda MAST; NRC G-881 NRC No. Grandiflora MAST; NRC alleles (PeeGee; Pee Gee) Greenspire AHN; MAST; NRC HC 970618 MAST Kyushu NRC Limelight NRC NA 74383 NRC Pee Wee NRC Phantom SN PI 479429 NCRPIP Pink Diamond NRC Pinky Winkyä NRC (DVPinky) Praecox MAST Silver Dollar NRC Tardiva AHN; NRC The Swanä (Barbara) NRC Unique AHN; NRC Webb NRC White Lace MAST White Lady NRC White Moth MAST; NRC White Tiara NRC zAHN = Amethyst Hill Nursery, Aurora, OR; genotypes. MAST = Stephen F. Austin MAST Arboretum, Nacogdoches, TX; NCRPIS = North Central Regional Plant Introduction Station, Ames, IA; NRC = Tennessee State University Nursery Research Center, McMinnville, TN; SN = H. paniculata Shadow Nursery, Winchester, TN. DNA was extracted from 1-cm2 pieces of fresh leaf tissue using a Qiagen Plant Mini Kit (Qiagen, Valencia, CA) and quantified using a NanoDrop Spectrophotometer (Nanodrop Technologies, Wilmington, DE). SSR amplification was performed using a modified three-primer protocol (Rinehart et al., 2006). Fluorescence-labeled polymer- ase chain reaction (PCR) fragments were visualized by automated capillary gel electro- phoresis on an ABI3100-Avant or ABI3730xl (Applied Biosystems, Foster City, CA) using ROX-500 size standard. GeneMapper ver- sion 4.0 (Applied Biosystems, Foster City, CA) was used to recognize and size peaks. SSR markers are described in Table 2 and all sequences were submitted to the Na- DQ521440 (TCA)8 AGAGGTCAGGCCTTGGAAAGATACDQ521451 (TCG)6 AGAGGTCAGGCCTTGGAAAGATAC CTTCTTCCTCTTCTTTGGTGGTTGDQ521449